In the field of recording weak illumination such as from astronomical phenomenon through telescopes the standard photographic plate of the past century has been replaced by electronic imaging techniques to overcome the problems of reciprocity and threshold sensitivities to faint celestial objects. While the photomultiplier tube is perhaps one of the most sensitive photoelectric light detectors its limitation to single point observation has required that scanning mechanisms be employed where a two-dimensional field of view is desired. The scanning has reduced the practicality of making long exposures. Other means for two-dimensional detection and recording of faint illumination include the use of two-dimensional sensor arrays. One particular example is the vidicon tube where a photoconductive target is exposed for an interval to low level radiation which registers a photoelectric pattern in the target representative of incident intensity. This registered pattern is converted to a sequence of electrical signals by scanning the target in adjacent scan lines. These prior art vidicon detector systems have exhibited many deficiencies which include a lack of sufficient dynamic range to detect the many magnitudes of variation in received celestial illumination, a lack of linearity in target response, a limited spectral response, and a low efficiency in the detector response.
Additionally, with the availability today of sophisticated image display and enhancement equipment and techniques it has become desirable to obtain records of low illumination level observations in a form suitable for storage, display and enhancement. Standard video recorders which have been used before to store an image are subject to amplitude and position error.